Can anyone help me sort out which bits from a Dualshock4 do what? Would like to add support of the ds4 to xboxdrv.

The ds4 does work with Linux, but buttons and axis are differently mapped to the accepted standard (x360), and quite a few games expect that mapping, without the ability to remap.
Failing adding support to xboxdrv... Does anyone know an alternative way to remap axis/buttons, which isn't jscal or one of those tools. Those also work, but still the above games won't use that remapped joystick (js0).

Using xboxdrv to remap the controls works, but only on the new device which the problematic games won't see/use.
Eg, Hotline Miami, Proteus, Stealth Basterd, Metro: Last Light. Serious Sam 3 doesn't see gamepads at all.
Teleglitch is the same but the creators will be adding sdl2 input libs soon.

SteamOS forums are unhelpful as there are very few "hardcore" or experienced people there.